Skeletal Maturity, Brace Compliance, and In-Brace Correction Rate Are Important Factors Associated with Cobb Angle Progression after Brace Treatment in Patients with Adolescent Idiopathic Scoliosis.

INTRODUCTION

This study investigated brace treatment for patients with adolescent idiopathic scoliosis (AIS) to comprehensively evaluate the factors associated with curve progression, including the effects of in-brace correction rate (ICR) and objective brace compliance. Additionally, it aimed to establish a clinically useful optimal ICR threshold for effective curve progression control.

METHODS

In this single-center retrospective analysis of prospectively collected data, 116 patients with AIS, with Cobb angles of 20°-40° and at least 1-year follow-up were included. Patients whose Cobb angles progressed by >5° were classified into the progressed group, whereas the others were categorized into the non-progressed group. Bracing time was objectively assessed using a thermometer.

RESULTS

In this study, 19 (16.4%) patients were assigned to the progressed group. Open triradiate cartilage was significantly more frequent in the progressed group (22.2% vs. 2.6%, p=0.011) whereas no significant differences were observed in demographics or pre-brace Cobb angles. The progressed group demonstrated a lower ICR (26.8% vs. 39.5%, p=0.002) and shorter bracing time at 6 months (14.0 hours vs. 17.4 hours, p=0.042). Multivariate logistic regression analysis revealed that Sanders grade (1-4), ICR, and bracing time were independently associated with Cobb angle progression (odds ratios: 7.01, 0.95, and 0.89, respectively; all p<0.05). Based on receiver operating characteristic curve analysis, the ICR threshold of 38.3% was identified to achieve a clinically significant negative predictive value of 95%.

CONCLUSIONS

Under objective bracing time monitoring, skeletal maturity, ICR, and bracing time were crucial factors in preventing curve progression 1 year after brace initiation in patients with Cobb angles of 20°-40°. An ICR of 38.3% is recommended as the target when bracing adjustments are feasible.